Waves Flashcards
Amplitude definition
The maximum disturbance from its undisturbed position.
Wavelength definition
The distance between a point on one wave and the same point on the next wave.
Time period definition
The time for one cycle of a wave to occur.
What is the difference between longitudinal and transverse waves?
- Transverse - the direction of the vibration is perpendicular to the direction of the wave.
- Longitudinal - the direction of the vibration is parallel to the direction of the wave.
Diffraction
- Diffraction happens when a wave passes an edge, passes through a narrow gap or goes past an object.
- Diffraction doesn’t change any of the properties of a wave.
- The only thing that changes is the direction in which the wave is travelling.
- The diffraction effect is greatest when the width of the gap is about the same size as the wavelength of the wave.
What is the wave equation?
v = f x λ speed = frequency x wavelength
Frequency deffinition
- The number of waves produced by a source each second.
* The number of waves that pass a certain point each second.
What is the electromagnetic spectrum?
- A continuous spectrum of waves.
- All the waves: transfer energy; are transverse; travel at the speed of light in a vacuum; can be reflected, refracted and diffracted.
What is the order of the electromagnetic spectrum in increasing frequency?
• Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays.
What is the order of the electromagnetic frequency increasing in wavelength?
• Gamma rays, x-rays, ultraviolet, visible light, infrared, microwaves, radio waves.
What is the order of the electromagnetic spectrum in increasing energy?
• Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays.
What is frequency measured in?
Hz
What are the uses and dangers of microwaves?
- Used for cooking (water molecules in food absorb microwaves and vibrate very quickly - heat is produced and conducted/connected to other parts).
- Used for mobile phone and satellite communications.
- Can heat human body tissue internally if there is not a shield to prevent microwaves from reaching the user.
What are the uses and dangers of infrared?
- Infrared is heat radiation, so infrared cameras can detect humans in collapsing buildings and finding criminals in darkness.
- Used in electrical heaters to keep people warm.
- Used in grills to cook food.
- If there is an over-exposure to infrared, it can cause skin burns.
What are the uses and dangers of visible light?
- Used for seeing things - cameras require it to take pictures.
- Too much can cause permanent damage to the retina (e.g. looking at the sun).
What are the uses and dangers of ultraviolet?
- UV rays are used in fluorescent lights to emit visible light (fluorescent lights are more energy efficient than filament light bulbs).
- Too much UV can cause skin cancer, skin blistering/burns and blindness.
What are the uses and dangers of x-rays?
- X-ray radiation is directed through humans to find broken bones, as x-rays can pass through flesh but not bone.
- Exposure can cause mutations leading to cancer.
What are the uses and dangers of gamma rays?
- Gamma rays can kill all the microbes on medical instruments, sterilising them (better than boiling instruments, as some might be plastic and could be damaged by the hot temperatures).
- Can sterilise food, keeping it fresh for longer.
- Because they have high energy and frequency, gamma rays can penetrate very far into the body and cause cell mutation/destruction, which can subsequently cause tissue damage or cancer.
What is the difference between analogue and digital signals?
- Analogue signals can take any value within a certain range. The amp,it use and frequency of an analogue wave can vary continuously.
- Digital signals can only take two values (on/off or 1/0).
What are the advantages of digital signals?
- Regeneration of digital signals, on the other hand, creates a clean and accurate copy of the original signal, because it is easy to tell what the original signal was.
- The signal therefore becomes much sharper as the noise is not amplified.
- Digital signals can carry more information.
What are the uses and dangers of radio waves?
- Used mainly for communication - long-, medium- and shirt-wave radio; TV.
- Possibly causes of cancer, leukaemia and other disorders.
What can ultrasound be used for?
- Cleaning surgical instruments.
- Treating muscle strains.
- Treating cataracts.
- Breaking up kidney stones.
- Dentistry.
- Body scans.
How does sound change when it has a smaller amplitude and frequency?
- Becomes quieter.
* Pitch decreases/more bass.
How do x-rays show an image of a bone?
The x-rays emitted from a scanner are absorbed by the bone and cannot pass through it.
